From: Martin Kronbichler <martin.kronbichler@uni-a.de>
Date: Tue, 31 May 2022 11:17:00 +0000 (+0200)
Subject: MatrixFree: Do not construct hanging nodes structure for non-adapted meshes
X-Git-Tag: v9.4.0-rc1~91^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d58492728abc4a314408799c2abb12d1899795f0;p=dealii.git

MatrixFree: Do not construct hanging nodes structure for non-adapted meshes
---

diff --git a/include/deal.II/matrix_free/hanging_nodes_internal.h b/include/deal.II/matrix_free/hanging_nodes_internal.h
index c946ad4339..d7bfbb3143 100644
--- a/include/deal.II/matrix_free/hanging_nodes_internal.h
+++ b/include/deal.II/matrix_free/hanging_nodes_internal.h
@@ -376,6 +376,17 @@ namespace internal
     inline void
     HangingNodes<3>::setup_line_to_cell(const Triangulation<3> &triangulation)
     {
+      // Check if we there are no hanging nodes on the current MPI process,
+      // which we do by checking if the second finest level holds no active
+      // non-artificial cell
+      if (triangulation.n_levels() <= 1 ||
+          std::none_of(triangulation.begin_active(triangulation.n_levels() - 2),
+                       triangulation.end_active(triangulation.n_levels() - 2),
+                       [](const CellAccessor<3, 3> &cell) {
+                         return !cell.is_artificial();
+                       }))
+        return;
+
       const unsigned int n_raw_lines = triangulation.n_raw_lines();
       this->line_to_cells.resize(n_raw_lines);